(1) Field of the Invention
This invention relates to new compositions of matter, particularly to Diels-Alder and ene adducts of phenolic-modified polyol esters of resin acids and more particularly to polyimide/polyamide phenolic-modified polyol esters derived therefrom which exhibit increased pigment dispersion efficiency, increased color development, and reduced bronzing in inks and related coatings.
(2) Description of the Prior Art
Lithographic inks consist primarily of pigments, natural and/or synthetic resins with high melting points (100.degree. to 200.degree. C.), alkyd resins, and hydrocarbon solvents. Low concentrations of plasticizers, antioxidants, chelates, pH modifiers, antiskinning agents, and other additives also are included in lithographic ink formulations.
The natural and synthetic high-melting resins are typically either petroleum-derived or wood-derived. Used solely or in combination, these resins are dissolved in the high-boiling hydrocarbon solvents to give homogeneous systems well known in the art as varnishes. Varnishes usually contain 20 to 70% resin solids. The alkyds, plasticizers, antioxidants, etc. are often included in the varnish, so that solids levels may exceed 70%.
It is known to those skilled in the art that in order to prepare phenolic resins, rosin may be reacted with phenols and formaldehyde to give phenol-rosin condensates which contain reactive double bonds and which may be reacted further in Diels-Alder and/or ene fashion with alpha, beta-unsaturated carbonyl compounds. These Diels-Alder and ene adducts of phenol-rosin condensates are then esterified with polyols to give broad molecular weight distribution resins with low residual acid number. This art is old and has been disclosed in numerous patents over the past decades.
Phenolic resins must meet several general requirements to be useful as lithographic ink resins. In order to make varnishes, for example, they must be capable of being dissolved in high-boiling hydrocarbon solvents to yield clear varnishes with manageable viscosities for easy workability. The varnishes must be stable in storage to viscosity, color, and clarity changes. On paper, the resin in the varnish or finished ink must dry to yield a durable, smooth, and uniform film with good resistance to abrasion and chemicals.
Moreover, it is appreciated that for phenolic resins to be useful as dispersing resins in lithographic ink pigment processing operations such as flushing, the resins must exhibit several specific properties in addition to the aforementioned requirements general to all lithographic ink resins. For example, when mixed with highly aqueous pigment presscake in high torque dough mixers commonly used for flushing operations, the resins present in the lithographic ink varnish must exhibit excellent pigment wetting properties. Such properties lead to rapid and thorough coverage of pigment particles present in the presscake and to the concurrent displacement of water originally bound to or entrained in the particle aggregates and agglomerates. Good wetting properties also lead to strong adhesion of resin to particle surfaces so that, as aggregates and agglomerates are broken down into primary particle units, resin will coat the particle surfaces thereby providing a steric barrier to particle-particle reaggregation and reagglomeration. Strong adhesion to and thorough coverage of surfaces of primary particle units by resin thus leads to increased color strength, gloss, and transparency, as well as reduced bronzing in the resulting pigment concentrate.
Strong pigment wetting characteristics are exhibited by compounds which have structures consisting of polar head groups attached to oleophilic tail segments. The polar head groups bind to the polar pigment particle surfaces while the oleophilic tail segments solubilize the bound particle with the continuous medium and also provide a steric barrier to particle-particle interactions.
Heretofore it was difficult with phenolic resins to impart this type of structure which enables strong pigment wetting characteristics. The known methods mentioned previously for preparing phenolic resins yield highly-crosslinked, nonuniform, three-dimensional resin molecules which do not meet the necessary structural requirement on the molecular level for enhanced pigment wetting. Via common synthetic methods, the only polar units present in phenolic resins are the hydroxyl and carboxyl functionalities; and these are sterically hindered within the highly-crosslinked, three-dimensional structure of the resin molecules; hence they are unavailable often for interaction with polar pigment particle surfaces.
From the prior art it is therefore apparent that polyol esters of the phenol-rosin condensates are prepared usually under methods which consist of reacting rosin with phenols and formaldehyde, followed by reaction with dienophiles and then subsequent esterification. Furthermore, from prior art descriptions, it is apparent that such synthetic methodologies lead to highly crosslinked, unordered, three-dimensional molecules which do not conform to structural requirements for good pigment wetting, namely they lack unhindered polar head groups attached to oleophilic tail segments.
Therefore, it is an object of the present invention to prepare novel Diels-Alder/ene adducts of polyol esters of phenol-rosin condensates.
It is another object of this invention to prepare novel polyimide/polyamide derivatives of the Diels-Alder/ene adducts of polyol esters of phenol-rosin condensates. It is another object of this invention to prepare Diels-Alder and ene adducts and their polyimide/polyamide derivatives from polyol esters of phenol-rosin condensates which are compatible with printing ink formulations.
It is still another object of this invention to prepare polyimide/polyamide derivatives of Diels-Alder and ene adducts of polyol esters of phenol-rosin condensates which have excellent pigment wetting characteristics as manifested in high water yields obtained during pigment dispersion operations known as flushing and as manifested in increased color strength, high gloss and low bronzing in pigment concentrates and in finished lithographic printing inks.